The present invention is directed to an air control for a lumbar support device of the type utilized in an automobile seat and more particularly to an air control for a lumbar support device wherein the air pressure of an air bag in a seat back is controlled by the opening and closing action of a spring biased check valve.
It is well known in the art to provide the seat back of an automobile seat with a plurality of horizontally disposed parallel air bags so that the curvature of the seat back can be adjusted by selectively regulating the air pressures in the individual air bags. In a conventional air control system, each air bag is uniformly provided with pressurized air from a common pressurized air source which is admitted through a check valve associated with each air bag. Subsequently, the air pressure in each air bag is selectively released to the atmosphere through its associated check valve through means of a suitable valve control device. Thus, the contour of the seat back may be varied for a particular individual by selectively reducing the air pressure in each of the air bags and controlling the rate of air pressure reduction in each air bag.
However, in those pressure control devices wherein the pressurized air is supplied to the air bags intermittently in a pulsating manner by means of a manual pump or the like, the check valves will be repeatedly opened and closed relative to the valve seat at high speeds. Such a hunting phenomenon related to fluctuation in the pressure of the supplied air results in an abnormal sound or noise being generated which creates a disagreeable or an annoying impression on the driver or a passenger.
In order to prevent the hunting action of a check valve, it has been previously proposed to utilize a spring guide member which is biased by means of a plate-type spring which acts as a damper due to sliding frictional resistence relative to a fixed member during displacement of the check valve. However, such an arrangement utilizing a plate-type damper has proven to be unsatisfactory since the spring load varies widely during manufacture as well as during use of the spring so that it is virtually impossible to set a predetermined pressure value for the opening action of the check valve.